Re: [lwip-users] Data sending problem over TCP

[Sanchayan]

Hi,

Thanks, Kieran for the help. Now, it has started working. I didn't have the 
knowledge of understanding the wireshark data. What you said, i also found 
in the lwip source code,  as below.

TCP RESET packet (empty segment with RST flag set) either to
* abort a connection or to show that there is no matching local connection
* for a received segment

We didn't have an appropriate front end utility so the connection was not 
getting established. One of my colleagues, wrote a Python source code for 
testing and what we were doing worked.

Thanks, Tim as well. Also, Tim can you elaborate your last post, of being 
careful when to call data outside of the interrupt context.

Thanks & Best Regards,
Sanchayan Maity.

----- Original Message ----- 
From: "Kieran Mansley" <address@hidden>
To: "Mailing list for lwIP users" <address@hidden>
Sent: Thursday, June 23, 2011 18:48
Subject: Re: [lwip-users] Data sending problem over TCP


> On Thu, 2011-06-23 at 15:10 +0530, Sanchayan wrote:
> > I have attached the wireshark .pcap file. And also a screenshot of
> > wireshark.
>
> That shows that the connection is being rejected by the host you're
> trying to connect to, probably because there is nothing listening on
> that port number.
>
> This should result in the tcp_err() callback being triggered to notify
> you that the connection has failed.  If it had succeeded the connected
> callback that you can pass to tcp_connect() would be called, but I
> notice that you're just giving it NULL instead.  If you take a look in
> doc/rawapi.txt there's a section there on how to use tcp_connect():
>
> - err_t tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr,
>                    u16_t port, err_t (* connected)(void *arg,
>                                                    struct tcp_pcb
> *tpcb,
>                                                    err_t err));
>
>  Sets up the pcb to connect to the remote host and sends the
>  initial SYN segment which opens the connection.
>
>  The tcp_connect() function returns immediately; it does not wait for
>  the connection to be properly setup. Instead, it will call the
>  function specified as the fourth argument (the "connected" argument)
>  when the connection is established. If the connection could not be
>  properly established, either because the other host refused the
>  connection or because the other host didn't answer, the "err"
>  callback function of this pcb (registered with tcp_err, see below)
>  will be called.
>
>  The tcp_connect() function can return ERR_MEM if no memory is
>  available for enqueueing the SYN segment. If the SYN indeed was
>  enqueued successfully, the tcp_connect() function returns ERR_OK.
>
> Kieran
>
>
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> https://lists.nongnu.org/mailman/listinfo/lwip-users 



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